After leaving wifi there is no mobile data - reboot is necessary

Hi all,
For some time now I have experienced that everytime I leave home and my wifi connection, my Fairphone 4 does not connect to mobile data - or that is: I cannot use the internet, using for instance my radio app and I will not receive any messages or notifications. Returning to wifi is not enough, I have to reboot the phone for it to connect.
Any suggestions for how to fix this? I have tried going through the app settings, making sure that I have not accidentially turned something off. I am not very tech savvy, but I am really not aware that I have done anything that could result in this annoying situation.
Best regards,

Try instead of rebooting switching Aeroplane mode on and off.

Sometimes it helps to remove the APN settings of the SIM card and enter them as new.

Thanks a lot for the answer and suggestion! Really appreciate it.

Yes, switching Aeroplane mode on and off would indeed be easier - but I would of course prefer not needing to do it at all. I have located the APN settings (did not know about this until now) and will try this out.